Sterling Reputation - Axle Upgrade Options

We have always had a bit of a contrarian streak. Maybe it was listening to too much Rage Against the Machine while growing up or always being told something could not be done. Whatever the cause, when it came time to sling a 1-ton axle under the rear of our latest Ford project, everyone recommended the venerable GM 14-bolt. So what did we go and do? We built a Sterling 10.5 axle that came under the rear of a Ford Super Duty.

How does a Sterling 10.5 stack up against a 14-bolt?

The main motivation was to match the metric bolt pattern (8x170 mm) on the front Dana 60 we are using, but the Sterling axle has other things going for it as well. While at Bayshore Truck adding Sierra gears and a Detroit Locker to our Sterling axle, we took the opportunity to see how it stacks up against the GM 14-bolt. You might be surprised at what we found.

Step By Step

1. We called up West Coast Differentials for a Detroit Locker and a 5.13 ring-and-pinion and install kit from Sierra Gear & Axle and stuffed them all under a heavy-duty cover from Ballistic Fabrication. WCD stocks everything you need for Sterling axles, 14-bolts, and most other applications.

2. Detroit Lockers are available from West Coast Differentials (WCD) for both the Sterling axle and the 14-bolt. The Sterling axle doesn’t have a carrier break, which is a good thing if you have already bought a Detroit with the stock gear ratio. Advantage: Tie.

3. If you are going through the trouble to lock or regear your axle it makes sense to use quality parts so you only have to do it once. We appreciate that the Sierra Gear install kit came with genuine American-made Timken bearings and not some cheap overseas product.

4. There is no comparison between the pinions on the two, so we won’t even make an argument for the Sterling axle. The pinion shaft, bearings, and teeth are all larger on the 14-bolt. Advantage: 14-bolt.

5. Even if all the other parts were equal, the biggest advantage the 14-bolt has is the third pinion bearing. It essentially eliminates gear deflection that often leads to breakage. Advantage: 14-bolt.

6. Not all Sterling pinions are created equal. Three styles have been used over the years. The early gearsets (right) used short splines on the pinion; the late gearsets (left) use a thinner pinion bearing. Don’t mix and match bearings and pinions between generations! They fit but will not function properly. Most aftermarket gearsets, like our 5.13s from Sierra, use the second-generation gears and bearings.

7. The ring gear diameter on the 14-bolt is slightly larger than the Sterling, and the pinion enters the housing at a lower location on the 14-bolt. This adds strength at the expense of driveline ground clearance. Sierra Gear offers a variety of gear ratios for both axles. Advantage: 14-bolt.

8. Both the Sterling and the 14-bolt use 11⁄2-inch axleshafts, but the Sterling uses 35 splines and the 14 bolt uses 30. Both are pretty darn strong, but 35 is still more than 30. Advantage: Sterling.

9. Both the Sterling and 14-bolt are full floaters, but the Sterling axle uses a much shorter spindle that places the bearings closer together, resulting in less load capacity. The Sterling axle does use one left-handed spindle nut though to keep the hub from coming loose when power is transferred through the axle. Advantage: Tie.

10. Rear disc brakes started coming standard on ’99 Super Duty trucks. They use solid rotors with a small drum inside to act as a parking brake. 14-bolts with factory discs are much less common, although they were offered starting with ’01 models and swap kits are available from sources like Offroad Design and Ballistic Fabrication for drum brake 14-bolts. Advantage: Sterling.

11. Our Sterling rear axle is 683⁄4 inches wide. Even wider 10.5 axles were available on E350 vans, many with a standard 8x61⁄2 bolt pattern. 14-bolt axles have come in a variety of widths over the years ranging from 63 to 72 inches, with 63 and 67 inches being the most common.

12. Our Sterling axle came with a flange on the pinion that accepts a 1410 U-joint and companion flange. Some prefer the flange to traditional yokes because there are no straps to come loose. 1350, 1410, and 1480 yokes and flanges are available for both the 14-bolt and Sterling axles.

13. Regardless of what diff you are running, Ballistic Fabrication probably makes a cover for it. Ballistic’s covers are made from laser-cut 3⁄8-inch formed steel that is welded inside and out. If you have a 14-bolt the company even offers a high-clearance cover as part of its shave kit.

14. Both are 1-ton axles and capable of supporting big tires, but with the 14-bolt big tires are a requirement since the bottom of the housing hangs down so far. Remember that shave kit we mentioned above? The Sterling doesn’t need much help since it provides 11⁄4 inches more ground clearance than the 14-bolt in stock form. Advantage: Sterling.

15. Bayshore takes a surface prep disc to every tooth on both the ring gear and the pinion before installation. The little details like this result in a quieter, cooler running gearset.

16. The shims provided by Sierra Gear & Axle have a collar on the inside (left) that allows you to stack the shim pack together without worrying about bending or spitting out shims when you put them in and out of the case. The 14-bolt uses threaded adjusters instead of shims, which ease installation. Advantage: 14-bolt.

17. The case had to come in and out a few times to get the correct pattern, but it didn’t phase Bayshore’s Aaron Lechner. He is methodical with his gear setup.